Heat transfer system



E. A. WEAVER HEAT TRANSFER SYSTEM Jan. 17, 1967 2 Sheets-Sheet 1 FiledJan. 11, 1965 FUZ L DEM/7ND HOTTEST souRCE 1: I

17; 1967 E. A. WEAVER 3,298,431

HEAT TRANSFER SYSTEM Filed Jan. 11, 1965 v 2 Sheets-Sheet 2 urru pzM/uvpF011 DEMAND I! I I HAIL (00155 7 SOURCE 0001.557 SOURCE United StatesPatent 3,298,431 HEAT TRANSFER SYSTEM Eastman A. Weaver, Wellesley,Mass, assignor to Comstock & Wescott, Inc., Cambridge, Mass, acorporation of Massachusetts Filed Jan. 11, 1965, Ser. No. 424,789 5Claims. (Cl. 165-105) This invention relates to the transfer of heatfrom a heat source to a heat sink and more particularly to heat transferfrom a heat-storage unit to a water heater. While any storage unit maybe employed in the system, the unit is preferably of the kind disclosedin the application of Richard E. Rice and William E, Whitney, Ser., No.391,-

676, filed August 24, 1964. Irrespective of the type of unit employedthe temperature of the unit varies through wide limits from a maximumwhen the unit is freshly charged with heat to a minimum when the unitcools to its lowest effective temperature. Also the rate at which heatshould be transferred to the water heater varies widely depending on therate at which that water is drawn from the heater.

Objects of the present invention are to provide a selfregulatory systemwhich is simple and economical to produce, which may be sealed from theatmosphere, which varies the rate of heat-transfer automatically inresponse to demand, from maximum to minimum temperature of the storageunit, and which is durable and reliable in use.

In one aspect the present invention involves a heat sink, a variableheat source, an endless conduit circuit in heat-transfer relation to thesource and sink for transferring heat from the source to the sink, thecircuit containing liquid vaporizable by the source and condensible bythe sink, the circuit including a sink-portion for holding fluid (liquidand/ or condensing vapor in heat-transfer relation to the sink, and asource-portion for holding a quantity of said liquid in varyingheat-transfer relation to the source, the sink being located above thesource so that the condensed liquid may drain back to or toward thesource by gravity through a return part of said circuit, a thermal valvein said return part of the circuit, and means responsive to thetemperature of the sink for substantially closing the valve when thetemperature of the sink reaches a predetermined maximum, saidsink-portion being large enough to contain substantially all of saidquantity, whereby when the sink reaches said maximum, substantially allof said quantity has been transferred to the sink-portion, therebysubstantially stopping heat-transfer from source to sink.

Preferably, the system has a by-pass around the aforesaid valve, and inthe bypass a check-valve which permits flow only from the source-portionto the sink-portion, and the system is sealed so that, when the thermalvalve is closed, the vapor-pressure in the source-portion forcessubstantially all the liquid in the source-portion through thecheck-valve to the sink-portion.

In another aspect the system comprises a heat sink, a variable heatsource, an endless conduit circuit in heattransfer relation to thesource and sink for transferring heat from the source to the sink, thecircuit containing liquid vaporizable by the source and condensible bythe sink, the circuit including a sink-portion for holding fluid inheat-transfer relation to the sink and a source-portion for holding aquantity of said liquid in variable heattransfer relation to the source,the sink being located above the source so that condensed liquid maydrain back to the source by gravity through a return part of saidcircuit, the circuit including a conduit for vapor flow from thesource-portion to the sink-portion, and thermostatic means in theconduit responsive to the temperature of the source for imposingresistance to the aforesaid vapor flow when the source is 'hot.Preferably, the aforesaid conduit 3,298,431 Patented Jan. 17, 1967comprises two branches in parrallel and the thermostatic means comprisesa valve for closing one branch.

The vaporizable liquid must not decompose in contact with the aforesaidcircuit wall when the source is at maximum temperature, e.g., 900 F. andneither the liquid nor its vapors should corrode the walls of thecircuit. Preferably the circuit is formed of stainless steel and theliquid comprises Water containing an anticor-rosive such as a chromate.

For the purpose of illustration a typical embodiment is shown in theaccompanying drawings in which the figures are diagrams showing theconditions in the system under different conditions of operation asfollows:

FIG. 1s0urce at maximum temperature and no demand for hot water;

FIG. 2-source at maximum temperature and maximum demand for hot Water;

FIG. 3source at minimum temperature and little demand for hot water;

FIG. 4source at minimum temperature and maximum demand for hot water,and

FIG. 5 shows a modified construction.

The particular embodiment chosen for the purpose of illustrationcomprises a heat-storage unit U, a water tank T and a sealed conduitcircuit containing water W and water vapor V. The circuit comprises asource-portion P1 surrounding the unit U, a sink-portion P2 surroundingthe tank T, a branched conduit C1 and C2 interconnecting the upper endsof the portions P1 and P2 and a branched conduit C3 and C4interconnecting the lower ends of the portions P1 and P2. Below the unitU is a reservoir R1 and below the tank T is a reservoir R2, thesereservoirs being large enough to hold much of the liquid out ofheattransfer relation to the tank and unit respectively. As illustratedthe reservoirs may constitute continuations of the portions P1 and P2respectively.

The system is sealed from the outside atmosphere but at the top of thecircuit is a safety-valve S to vent the system in case of excessivepressure.

In the conduit C2 is a thermostatic valve V1 controlled by thetemperature of the heat unit U the valve being closed when the heat unitis freshly charged and gradually opening as the temperature of the unitdecreases from maximum to minimum. Thus when the unit is at maximumtemperature, vapor can flow only through conduit C1 but as thetemperature of the unit decreases an increasing amount of vapor can flowthrough conduit C2 in parallel with C1. Thus the fiow of vapor isautomatically controlled by the temperature of the unit U so that theflow corresponds to the need irrespective of the temperature of the unitU. In the illustration valve V1 is closed in FIGS. 1 and 2 and open inFIGS. 3 and 4.

In the conduit C3 is a thermostatic valve V2 controlled by thetemperature of the water in tank T. When the water is at maximumtemperature the valve is closed so that the liquid in P2 may rise to thelevel L1 (FIG. 1) thereby obstructing vapor from reaching tank T andstopping heat transfer to the tank. When the tank begins to cool valveV2 gradually opens, permitting the level L1 to fall and thereby exposingthe tank to condensing vapor.

In conduit C4 is a check-valve V3 which permits flow only in thedirection of the arrow. Thus when tank T reaches maximum temperature andno water is being drawn from the tank the vapor pressure forces liquidfrom the reservoir R1 upwardly through conduit C5 to reservoir R2 andP2, causing the liquid in P1 and R1 to fall to a level L2 (FIG. 1)practically out of heat-transfer relation to the unit U and therebysubstantial-1y stopping vaporization.

When water is drawn from tank T the temperature of the water at thebottom of the tank drops and the valve V2 opens, thereby permittingwater to flow downwardly through conduit C5, lowering level L1 to L3 andraising level L2 to L4 ('FIG. 2). When the unit U is relatively cooland. little water is being drawn from tank T the liquid in P1 stands ata level L5 in heat-transfer relation to only a part of the unit U, andthe liquid in reservoir R2 stands at a corresponding level L6 (FIG. 3).As demand increases valve V2 opens to permit liquid to flow fromreservoir R2 to R1 and P1, thereby producing levels L7 and L8 such asillustrated in FIG. 4 where the liquid is in heat-transfer relation tothe entire unit U.

As shown in FIG. 5 the outlet from conduit C5 to reservoir R1 may beabove the bottom of the reservoir and a wick K may be anchored in theconduit to minimize pressure surges. Also the walls of reservoir R1 maybe corrugated to increase the length of the conductive path from thebottom of the unit U to the level L2, thereby to minimize vaporizationwhen the liquid is at this low level as in FIG. 1.

It should be understood that the present disclosure is for the purposeof illustration only and that this invention includes all modificationsand equivalents which fall within the scope of the appended claims.

I claim:

1. A heat-transfer system comprising a :heat sink, a variable heatsource the temperature of which varies throughout a wide range, anendless conduit circuit in heat-transfer relation to the source and sinkfor transferring heat from the source to the sink, the circuitcontaining liquid vaporizable by the source and condensible by the sink,the circuit including a sink-portion for holding liquid in heat-transferrelation to the sink and a source-portion for holding a quantity of saidliquid in heat-transfer relation to the source and a return-portionleading from the lower end of the source-portion, the sink being locatedabove the source so that the condensed liquid may drain back to thesource by gravity through said return portion of said circuit, a thermalvalve in said return-portion of the circuit, means responsive to thetemperature of the sink for substantially closing the valve when thetemperature of the sink reaches a predetermined maximum, saidsink-portion being large enough to contain substantially all of saidquantity, whereby when the sink reaches said maximum substantially allof said quantity is transferred to the sink-portion therebysubstantially stopping heat-transfer from source to sink, a by-passaround said valve and in the by-pass a check-valve which permits flowonly from said sourceportion to said sink-portion, and the system beingsealed so that, when said thermal valve is closed, the vapor pres surein the source-portion produced by said source may force substantiallyall the liquid in the source-portion through the check-valve to thesink-portion.

2. A heat-transfer system comprising a heat sink, a variable heat sourcethe temperature of which varies throughout a wide range, an endlessconduit circuit in heat-transfer relation to the source and sink fortransfering heat from the source to the sink, the circuit containingliquid vaporizable by the source and condensible by the sink, thecircuit including a sink-portion for holding liquid in heat-transferrelation to the sink and a source-portion for holding a quantity of saidliquid in heat-transfer relation to the source, the sink being locatedabove the source so that the condensed liquid may drain back to thesource by gravity through a return part of said circuit, the circuitincluding a conduit for vapor flow from the source-portion to thesink-portion, and means in said conduit responsive to the temperature ofthe source for gradually increasing resistance to said vapor flow as thetemperature of the source rises.

3. A heat-transfer system according to claim 2 wherein said conduitcomprises two branches in parallel and said means comprises a valve forclosing one branch.

4. A heat-transfer system according to claim 1 further characterized bya conduit for vapor flow from the sourceportion to the sink-portion, andmeans in said conduit responsive to the temperature of the source forimposing resistance to said vapor flow as the tem erature of the sourcerises.

5. A heat-transfer system according to claim 4 wherein said conduitcomprises two branches in parallel and said means comprises a valve forclosing one branch.

References Cited by the Examiner UNITED STATES PATENTS 1,975,868 10/1934Schlumbohm 62-333 X 2,083,611 6/1937 Marshall --39 X FOREIGN PATENTS738,056 10/1932 France. 589,618 12/1933 Germany.

ROBERT A. OLEARY, Primary Examiner.

N. R. WILSON, Assistant Examiner.

1. A HEAT-TRANSFER SYSTEM COMPRISING A HEAT SINK, A VARIABLE HEAT SOURCETHE TEMPERATURE OF WHICH VARIES THROUGHOUT A WIDE RANGE, AN ENDLESSCONDUIT CIRCUIT IN HEAT-TRANSFER RELATION TO THE SOURCE AND SINK FORTRANSFERRING HEAT FROM THE SOURCE TO THE SINK, THE CIRCUIT CONTAININGLIQUID VAPORIZABLE BY THE SOURCE AND CONDENSIBLE BY THE SINK, THECIRCUIT INCLUDING A SINK-PORTION FOR HOLDING LIQUID IN HEAT-TRANSFERRELATION TO THE SINK AND A SOURCE-PORTION FOR HOLDING A QUALITY OF SAIDLIQUID IN HEAT-TRANSFER RELATION TO THE SOURCE AND A RETURN-PORTIONLEADING FROM THE LOWER END OF THE SOURCE-PORTION, THE SINK BEING LOCATEDABOVE THE SOURCE SO THAT THE CONDENSED LIQUID MAY DRAIN BACK TO THESOURCE BY GRAVITY THROUGH SAID RETURN PORTION OF SAID CIRCUIT, A THERMALVALVE IN SAID RETURN-PORTION OF THE CIRCUIT, MEANS RESPONSIVE TO THETEMPERATURE OF THE SINK FOR SUBSTANTIALLY CLOSING THE VALVE WHEN THETEMPERATURE OF THE SINK REACHES A PREDETERMINED MAXIMUM, SAIDSINK-PORTION BEING LARGE ENOUGH TO CONTAIN SUBSTANTIALLY ALL OF SAIDQUANTITY, WHEREBY WHEN THE SINK REACHES SAID MAXIMUM SUBSTANTIALLY ALLOF SAID QUANTITY IS TRANSFERRED TO THE SINK-PORTION THEREBYSUBSTANTIALLY STOPPING HEAT-TRANSFER FROM SOURCE TO SINK, A BY-PASSAROUND SAID VALVE AND IN THE BY-PASS A CHECK-VALVE WHICH PERMITS FLOWONLY FROM SAID SOURCE-